Three years of being with someone is a long time. It's going to take time even if it came to a calm end. I'm glad the two of you are still talking and are friends. I think that's going to be important in bringing closure to both of you. It's nice to see that the mutual respect, support and caring is still there. So, I hope you realize
that in itself says something pretty incredible about you. I really respect that.
I can't really speak personally about rebounds or breakups. But, I can speak about over-thinking/over-analyzing.
I do a lot of self-reflection and I have found that sometimes I need to give myself a break. It's almost like you have to let your mind rest and let things naturally balance themselves.
You might also want to explore some independent activities like running/jogging or meditating to slowly get yourself back to enjoying solitude again. Maybe get outside and lay in the sun?
As the self-analyzing type, you also probably knew already during the course of the relationship what was happening. There might not be anything "new" right now for you to figure out.
So, I would just focus on things to help you relax.